/** @license
 * DHTML Snowstorm! JavaScript-based snow for web pages
 * Making it snow on the internets since 2003. You're welcome.
 * -----------------------------------------------------------
 * Version 1.44.20131215 (Previous rev: 1.44.20131208)
 * Copyright (c) 2007, Scott Schiller. All rights reserved.
 * Code provided under the BSD License
 * http://schillmania.com/projects/snowstorm/license.txt
 */

/*jslint nomen: true, plusplus: true, sloppy: true, vars: true, white: true */
/*global window, document, navigator, clearInterval, setInterval */

var snowStorm = (function(window, document) {

	// --- common properties ---

	this.autoStart = true;          // Whether the snow should start automatically or not.
	this.excludeMobile = true;      // Snow is likely to be bad news for mobile phones' CPUs (and batteries.) Enable at your own risk.
	this.flakesMax = 128;           // Limit total amount of snow made (falling + sticking)
	this.flakesMaxActive = 64;      // Limit amount of snow falling at once (less = lower CPU use)
	this.animationInterval = 33;    // Theoretical "miliseconds per frame" measurement. 20 = fast + smooth, but high CPU use. 50 = more conservative, but slower
	this.useGPU = true;             // Enable transform-based hardware acceleration, reduce CPU load.
	this.className = null;          // CSS class name for further customization on snow elements
	this.excludeMobile = true;      // Snow is likely to be bad news for mobile phones' CPUs (and batteries.) By default, be nice.
	this.flakeBottom = null;        // Integer for Y axis snow limit, 0 or null for "full-screen" snow effect
	this.followMouse = true;        // Snow movement can respond to the user's mouse
	this.snowColor = '#F00';        // Don't eat (or use?) yellow snow.
	this.snowCharacter = '&bull;';  // &bull; = bullet, &middot; is square on some systems etc.
	this.snowStick = true;          // Whether or not snow should "stick" at the bottom. When off, will never collect.
	this.targetElement = null;      // element which snow will be appended to (null = document.body) - can be an element ID eg. 'myDiv', or a DOM node reference
	this.useMeltEffect = true;      // When recycling fallen snow (or rarely, when falling), have it "melt" and fade out if browser supports it
	this.useTwinkleEffect = false;  // Allow snow to randomly "flicker" in and out of view while falling
	this.usePositionFixed = false;  // true = snow does not shift vertically when scrolling. May increase CPU load, disabled by default - if enabled, used only where supported
	this.usePixelPosition = false;  // Whether to use pixel values for snow top/left vs. percentages. Auto-enabled if body is position:relative or targetElement is specified.

	// --- less-used bits ---

	this.freezeOnBlur = true;       // Only snow when the window is in focus (foreground.) Saves CPU.
	this.flakeLeftOffset = 0;       // Left margin/gutter space on edge of container (eg. browser window.) Bump up these values if seeing horizontal scrollbars.
	this.flakeRightOffset = 0;      // Right margin/gutter space on edge of container
	this.flakeWidth = 8;            // Max pixel width reserved for snow element
	this.flakeHeight = 8;           // Max pixel height reserved for snow element
	this.vMaxX = 5;                 // Maximum X velocity range for snow
	this.vMaxY = 4;                 // Maximum Y velocity range for snow
	this.zIndex = 0;                // CSS stacking order applied to each snowflake

	// --- "No user-serviceable parts inside" past this point, yadda yadda ---

	var storm = this,
	features,
	// UA sniffing and backCompat rendering mode checks for fixed position, etc.
	isIE = navigator.userAgent.match(/msie/i),
	isIE6 = navigator.userAgent.match(/msie 6/i),
	isMobile = navigator.userAgent.match(/mobile|opera m(ob|in)/i),
	isBackCompatIE = (isIE && document.compatMode === 'BackCompat'),
	noFixed = (isBackCompatIE || isIE6),
	screenX = null, screenX2 = null, screenY = null, scrollY = null, docHeight = null, vRndX = null, vRndY = null,
	windOffset = 1,
	windMultiplier = 2,
	flakeTypes = 6,
	fixedForEverything = false,
	targetElementIsRelative = false,
	opacitySupported = (function(){
		try {
			document.createElement('div').style.opacity = '0.5';
		} catch(e) {
			return false;
		}
		return true;
	}()),
	didInit = false,
	docFrag = document.createDocumentFragment();

	features = (function() {

		var getAnimationFrame;

		/**
		 * hat tip: paul irish
		 * http://paulirish.com/2011/requestanimationframe-for-smart-animating/
		 * https://gist.github.com/838785
		 */

		function timeoutShim(callback) {
			window.setTimeout(callback, 1000/(storm.animationInterval || 20));
		}

		var _animationFrame = (window.requestAnimationFrame ||
				window.webkitRequestAnimationFrame ||
				window.mozRequestAnimationFrame ||
				window.oRequestAnimationFrame ||
				window.msRequestAnimationFrame ||
				timeoutShim);

		// apply to window, avoid "illegal invocation" errors in Chrome
		getAnimationFrame = _animationFrame ? function() {
			return _animationFrame.apply(window, arguments);
		} : null;

		var testDiv;

		testDiv = document.createElement('div');

		function has(prop) {

			// test for feature support
			var result = testDiv.style[prop];
			return (result !== undefined ? prop : null);

		}

		// note local scope.
		var localFeatures = {

			transform: {
				ie:  has('-ms-transform'),
				moz: has('MozTransform'),
				opera: has('OTransform'),
				webkit: has('webkitTransform'),
				w3: has('transform'),
				prop: null // the normalized property value
			},

			getAnimationFrame: getAnimationFrame

		};

		localFeatures.transform.prop = (
			localFeatures.transform.w3 ||
			localFeatures.transform.moz ||
			localFeatures.transform.webkit ||
			localFeatures.transform.ie ||
			localFeatures.transform.opera
		);

		testDiv = null;

		return localFeatures;

	}());

	this.timer = null;
	this.flakes = [];
	this.disabled = false;
	this.active = false;
	this.meltFrameCount = 20;
	this.meltFrames = [];

	this.setXY = function(o, x, y) {

		if (!o) {
			return false;
		}

		if (storm.usePixelPosition || targetElementIsRelative) {

			o.style.left = (x - storm.flakeWidth) + 'px';
			o.style.top = (y - storm.flakeHeight) + 'px';

		} else if (noFixed) {

			o.style.right = (100-(x/screenX*100)) + '%';
			// avoid creating vertical scrollbars
			o.style.top = (Math.min(y, docHeight-storm.flakeHeight)) + 'px';

		} else {

			if (!storm.flakeBottom) {

				// if not using a fixed bottom coordinate...
				o.style.right = (100-(x/screenX*100)) + '%';
				o.style.bottom = (100-(y/screenY*100)) + '%';

			} else {

				// absolute top.
				o.style.right = (100-(x/screenX*100)) + '%';
				o.style.top = (Math.min(y, docHeight-storm.flakeHeight)) + 'px';

			}

		}

	};

	this.events = (function() {

		var old = (!window.addEventListener && window.attachEvent), slice = Array.prototype.slice,
		evt = {
			add: (old?'attachEvent':'addEventListener'),
			remove: (old?'detachEvent':'removeEventListener')
		};

		function getArgs(oArgs) {
			var args = slice.call(oArgs), len = args.length;
			if (old) {
				args[1] = 'on' + args[1]; // prefix
				if (len > 3) {
					args.pop(); // no capture
				}
			} else if (len === 3) {
				args.push(false);
			}
			return args;
		}

		function apply(args, sType) {
			var element = args.shift(),
					method = [evt[sType]];
			if (old) {
				element[method](args[0], args[1]);
			} else {
				element[method].apply(element, args);
			}
		}

		function addEvent() {
			apply(getArgs(arguments), 'add');
		}

		function removeEvent() {
			apply(getArgs(arguments), 'remove');
		}

		return {
			add: addEvent,
			remove: removeEvent
		};

	}());

	function rnd(n,min) {
		if (isNaN(min)) {
			min = 0;
		}
		return (Math.random()*n)+min;
	}

	function plusMinus(n) {
		return (parseInt(rnd(2),10)===1?n*-1:n);
	}

	this.randomizeWind = function() {
		var i;
		vRndX = plusMinus(rnd(storm.vMaxX,0.2));
		vRndY = rnd(storm.vMaxY,0.2);
		if (this.flakes) {
			for (i=0; i<this.flakes.length; i++) {
				if (this.flakes[i].active) {
					this.flakes[i].setVelocities();
				}
			}
		}
	};

	this.scrollHandler = function() {
		var i;
		// "attach" snowflakes to bottom of window if no absolute bottom value was given
		scrollY = (storm.flakeBottom ? 0 : parseInt(window.scrollY || document.documentElement.scrollTop || (noFixed ? document.body.scrollTop : 0), 10));
		if (isNaN(scrollY)) {
			scrollY = 0; // Netscape 6 scroll fix
		}
		if (!fixedForEverything && !storm.flakeBottom && storm.flakes) {
			for (i=0; i<storm.flakes.length; i++) {
				if (storm.flakes[i].active === 0) {
					storm.flakes[i].stick();
				}
			}
		}
	};

	this.resizeHandler = function() {
		if (window.innerWidth || window.innerHeight) {
			screenX = window.innerWidth - 16 - storm.flakeRightOffset;
			screenY = (storm.flakeBottom || window.innerHeight);
		} else {
			screenX = (document.documentElement.clientWidth || document.body.clientWidth || document.body.scrollWidth) - (!isIE ? 8 : 0) - storm.flakeRightOffset;
			screenY = storm.flakeBottom || document.documentElement.clientHeight || document.body.clientHeight || document.body.scrollHeight;
		}
		docHeight = document.body.offsetHeight;
		screenX2 = parseInt(screenX/2,10);
	};

	this.resizeHandlerAlt = function() {
		screenX = storm.targetElement.offsetWidth - storm.flakeRightOffset;
		screenY = storm.flakeBottom || storm.targetElement.offsetHeight;
		screenX2 = parseInt(screenX/2,10);
		docHeight = document.body.offsetHeight;
	};

	this.freeze = function() {
		// pause animation
		if (!storm.disabled) {
			storm.disabled = 1;
		} else {
			return false;
		}
		storm.timer = null;
	};

	this.resume = function() {
		if (storm.disabled) {
			 storm.disabled = 0;
		} else {
			return false;
		}
		storm.timerInit();
	};

	this.toggleSnow = function() {
		if (!storm.flakes.length) {
			// first run
			storm.start();
		} else {
			storm.active = !storm.active;
			if (storm.active) {
				storm.show();
				storm.resume();
			} else {
				storm.stop();
				storm.freeze();
			}
		}
	};

	this.stop = function() {
		var i;
		this.freeze();
		for (i=0; i<this.flakes.length; i++) {
			this.flakes[i].o.style.display = 'none';
		}
		storm.events.remove(window,'scroll',storm.scrollHandler);
		storm.events.remove(window,'resize',storm.resizeHandler);
		if (storm.freezeOnBlur) {
			if (isIE) {
				storm.events.remove(document,'focusout',storm.freeze);
				storm.events.remove(document,'focusin',storm.resume);
			} else {
				storm.events.remove(window,'blur',storm.freeze);
				storm.events.remove(window,'focus',storm.resume);
			}
		}
	};

	this.show = function() {
		var i;
		for (i=0; i<this.flakes.length; i++) {
			this.flakes[i].o.style.display = 'block';
		}
	};

	this.SnowFlake = function(type,x,y) {
		var s = this;
		this.type = type;
		this.x = x||parseInt(rnd(screenX-20),10);
		this.y = (!isNaN(y)?y:-rnd(screenY)-12);
		this.vX = null;
		this.vY = null;
		this.vAmpTypes = [1,1.2,1.4,1.6,1.8]; // "amplification" for vX/vY (based on flake size/type)
		this.vAmp = this.vAmpTypes[this.type] || 1;
		this.melting = false;
		this.meltFrameCount = storm.meltFrameCount;
		this.meltFrames = storm.meltFrames;
		this.meltFrame = 0;
		this.twinkleFrame = 0;
		this.active = 1;
		this.fontSize = (10+(this.type/5)*10);
		this.o = document.createElement('div');
		this.o.innerHTML = storm.snowCharacter;
		if (storm.className) {
			this.o.setAttribute('class', storm.className);
		}
		this.o.style.color = storm.snowColor;
		this.o.style.position = (fixedForEverything?'fixed':'absolute');
		if (storm.useGPU && features.transform.prop) {
			// GPU-accelerated snow.
			this.o.style[features.transform.prop] = 'translate3d(0px, 0px, 0px)';
		}
		this.o.style.width = storm.flakeWidth+'px';
		this.o.style.height = storm.flakeHeight+'px';
		this.o.style.fontFamily = 'arial,verdana';
		this.o.style.cursor = 'default';
		this.o.style.overflow = 'hidden';
		this.o.style.fontWeight = 'normal';
		this.o.style.zIndex = storm.zIndex;
		docFrag.appendChild(this.o);

		this.refresh = function() {
			if (isNaN(s.x) || isNaN(s.y)) {
				// safety check
				return false;
			}
			storm.setXY(s.o, s.x, s.y);
		};

		this.stick = function() {
			if (noFixed || (storm.targetElement !== document.documentElement && storm.targetElement !== document.body)) {
				s.o.style.top = (screenY+scrollY-storm.flakeHeight)+'px';
			} else if (storm.flakeBottom) {
				s.o.style.top = storm.flakeBottom+'px';
			} else {
				s.o.style.display = 'none';
				s.o.style.top = 'auto';
				s.o.style.bottom = '0%';
				s.o.style.position = 'fixed';
				s.o.style.display = 'block';
			}
		};

		this.vCheck = function() {
			if (s.vX>=0 && s.vX<0.2) {
				s.vX = 0.2;
			} else if (s.vX<0 && s.vX>-0.2) {
				s.vX = -0.2;
			}
			if (s.vY>=0 && s.vY<0.2) {
				s.vY = 0.2;
			}
		};

		this.move = function() {
			var vX = s.vX*windOffset, yDiff;
			s.x += vX;
			s.y += (s.vY*s.vAmp);
			if (s.x >= screenX || screenX-s.x < storm.flakeWidth) { // X-axis scroll check
				s.x = 0;
			} else if (vX < 0 && s.x-storm.flakeLeftOffset < -storm.flakeWidth) {
				s.x = screenX-storm.flakeWidth-1; // flakeWidth;
			}
			s.refresh();
			yDiff = screenY+scrollY-s.y+storm.flakeHeight;
			if (yDiff<storm.flakeHeight) {
				s.active = 0;
				if (storm.snowStick) {
					s.stick();
				} else {
					s.recycle();
				}
			} else {
				if (storm.useMeltEffect && s.active && s.type < 3 && !s.melting && Math.random()>0.998) {
					// ~1/1000 chance of melting mid-air, with each frame
					s.melting = true;
					s.melt();
					// only incrementally melt one frame
					// s.melting = false;
				}
				if (storm.useTwinkleEffect) {
					if (s.twinkleFrame < 0) {
						if (Math.random() > 0.97) {
							s.twinkleFrame = parseInt(Math.random() * 8, 10);
						}
					} else {
						s.twinkleFrame--;
						if (!opacitySupported) {
							s.o.style.visibility = (s.twinkleFrame && s.twinkleFrame % 2 === 0 ? 'hidden' : 'visible');
						} else {
							s.o.style.opacity = (s.twinkleFrame && s.twinkleFrame % 2 === 0 ? 0 : 1);
						}
					}
				}
			}
		};

		this.animate = function() {
			// main animation loop
			// move, check status, die etc.
			s.move();
		};

		this.setVelocities = function() {
			s.vX = vRndX+rnd(storm.vMaxX*0.12,0.1);
			s.vY = vRndY+rnd(storm.vMaxY*0.12,0.1);
		};

		this.setOpacity = function(o,opacity) {
			if (!opacitySupported) {
				return false;
			}
			o.style.opacity = opacity;
		};

		this.melt = function() {
			if (!storm.useMeltEffect || !s.melting) {
				s.recycle();
			} else {
				if (s.meltFrame < s.meltFrameCount) {
					s.setOpacity(s.o,s.meltFrames[s.meltFrame]);
					s.o.style.fontSize = s.fontSize-(s.fontSize*(s.meltFrame/s.meltFrameCount))+'px';
					s.o.style.lineHeight = storm.flakeHeight+2+(storm.flakeHeight*0.75*(s.meltFrame/s.meltFrameCount))+'px';
					s.meltFrame++;
				} else {
					s.recycle();
				}
			}
		};

		this.recycle = function() {
			s.o.style.display = 'none';
			s.o.style.position = (fixedForEverything?'fixed':'absolute');
			s.o.style.bottom = 'auto';
			s.setVelocities();
			s.vCheck();
			s.meltFrame = 0;
			s.melting = false;
			s.setOpacity(s.o,1);
			s.o.style.padding = '0px';
			s.o.style.margin = '0px';
			s.o.style.fontSize = s.fontSize+'px';
			s.o.style.lineHeight = (storm.flakeHeight+2)+'px';
			s.o.style.textAlign = 'center';
			s.o.style.verticalAlign = 'baseline';
			s.x = parseInt(rnd(screenX-storm.flakeWidth-20),10);
			s.y = parseInt(rnd(screenY)*-1,10)-storm.flakeHeight;
			s.refresh();
			s.o.style.display = 'block';
			s.active = 1;
		};

		this.recycle(); // set up x/y coords etc.
		this.refresh();

	};

	this.snow = function() {
		var active = 0, flake = null, i, j;
		for (i=0, j=storm.flakes.length; i<j; i++) {
			if (storm.flakes[i].active === 1) {
				storm.flakes[i].move();
				active++;
			}
			if (storm.flakes[i].melting) {
				storm.flakes[i].melt();
			}
		}
		if (active<storm.flakesMaxActive) {
			flake = storm.flakes[parseInt(rnd(storm.flakes.length),10)];
			if (flake.active === 0) {
				flake.melting = true;
			}
		}
		if (storm.timer) {
			features.getAnimationFrame(storm.snow);
		}
	};

	this.mouseMove = function(e) {
		if (!storm.followMouse) {
			return true;
		}
		var x = parseInt(e.clientX,10);
		if (x<screenX2) {
			windOffset = -windMultiplier+(x/screenX2*windMultiplier);
		} else {
			x -= screenX2;
			windOffset = (x/screenX2)*windMultiplier;
		}
	};

	this.createSnow = function(limit,allowInactive) {
		var i;
		for (i=0; i<limit; i++) {
			storm.flakes[storm.flakes.length] = new storm.SnowFlake(parseInt(rnd(flakeTypes),10));
			if (allowInactive || i>storm.flakesMaxActive) {
				storm.flakes[storm.flakes.length-1].active = -1;
			}
		}
		storm.targetElement.appendChild(docFrag);
	};

	this.timerInit = function() {
		storm.timer = true;
		storm.snow();
	};

	this.init = function() {
		var i;
		for (i=0; i<storm.meltFrameCount; i++) {
			storm.meltFrames.push(1-(i/storm.meltFrameCount));
		}
		storm.randomizeWind();
		storm.createSnow(storm.flakesMax); // create initial batch
		storm.events.add(window,'resize',storm.resizeHandler);
		storm.events.add(window,'scroll',storm.scrollHandler);
		if (storm.freezeOnBlur) {
			if (isIE) {
				storm.events.add(document,'focusout',storm.freeze);
				storm.events.add(document,'focusin',storm.resume);
			} else {
				storm.events.add(window,'blur',storm.freeze);
				storm.events.add(window,'focus',storm.resume);
			}
		}
		storm.resizeHandler();
		storm.scrollHandler();
		if (storm.followMouse) {
			storm.events.add(isIE?document:window,'mousemove',storm.mouseMove);
		}
		storm.animationInterval = Math.max(20,storm.animationInterval);
		storm.timerInit();
	};

	this.start = function(bFromOnLoad) {
		if (!didInit) {
			didInit = true;
		} else if (bFromOnLoad) {
			// already loaded and running
			return true;
		}
		if (typeof storm.targetElement === 'string') {
			var targetID = storm.targetElement;
			storm.targetElement = document.getElementById(targetID);
			if (!storm.targetElement) {
				throw new Error('Snowstorm: Unable to get targetElement "'+targetID+'"');
			}
		}
		if (!storm.targetElement) {
			storm.targetElement = (document.body || document.documentElement);
		}
		if (storm.targetElement !== document.documentElement && storm.targetElement !== document.body) {
			// re-map handler to get element instead of screen dimensions
			storm.resizeHandler = storm.resizeHandlerAlt;
			//and force-enable pixel positioning
			storm.usePixelPosition = true;
		}
		storm.resizeHandler(); // get bounding box elements
		storm.usePositionFixed = (storm.usePositionFixed && !noFixed && !storm.flakeBottom); // whether or not position:fixed is to be used
		if (window.getComputedStyle) {
			// attempt to determine if body or user-specified snow parent element is relatlively-positioned.
			try {
				targetElementIsRelative = (window.getComputedStyle(storm.targetElement, null).getPropertyValue('position') === 'relative');
			} catch(e) {
				// oh well
				targetElementIsRelative = false;
			}
		}
		fixedForEverything = storm.usePositionFixed;
		if (screenX && screenY && !storm.disabled) {
			storm.init();
			storm.active = true;
		}
	};

	function doDelayedStart() {
		window.setTimeout(function() {
			storm.start(true);
		}, 20);
		// event cleanup
		storm.events.remove(isIE?document:window,'mousemove',doDelayedStart);
	}

	function doStart() {
		if (!storm.excludeMobile || !isMobile) {
			doDelayedStart();
		}
		// event cleanup
		storm.events.remove(window, 'load', doStart);
	}

	// hooks for starting the snow
	if (storm.autoStart) {
		storm.events.add(window, 'load', doStart, false);
	}

	return this;

}(window, document));
